Chapter 4 Modeling Systems with Processes and Basic Entity Flow


By the end of this chapter, students should be able to:

  • Gain a deeper understanding of the application of attributes and variables within models

  • Understand what expressions are and how they can be applied within models

  • Understand when ROUTE, STATION, and SEQUENCE modules can be used and apply them effectively for simple network modeling situations

  • To be able to understand and model shared resources

  • To be able to understand and model the duplication and batching of entities

Recall from Chapter 2 that a process is a sequence of activities experienced by entities as they move through a system. Activities represent tasks that take time and may require resources. We saw in Chapter 3 how to expand on process modeling by building a model of a STEM mixer. In that modeling, there were a number of activities (getting the name tag, wandering around, visiting with recruiters) that were modeled with basic modeling constructs such as SEIZE, DELAY, RELEASE. In addition, we saw how to use the DECIDE and LABEL modules to direct the flow of entities within a model. Chapter 3 also introduced the common statistical quantities produced by simulation models and provided an overview for how to plan for the execution of the model by determining the size of the sample for the experiments. In this chapter, the basic modeling concepts of Chapter 2 and 3 will be expanded on to allow you to model situations involving the movement of entities within a system. Specifically, we will introduce, through an expanded version of the STEM mixer, the notion of modeling locations in the physical world where processing occurs. This will be based on the use of the STATION module. Then, we will be able to model movement between locations (stations) via the transfer of entities by the ROUTE module. These modules will essentially replace the LABEL and GOTO LABEL modules of Chapter 3. Some additional animation elements will also be introduced. Finally, in additional models, we will see how to model processes that occur in parallel and how to share resources between activities. We will start with the enhanced STEM Career Mixer example.